1. Field of the Invention
The present invention relates to an endoscope wherein an image pick-up unit and a channel tube are built in a distal end forming portion.
2. Description of the Related Art
An endoscope includes an elongate insertion portion configured to be inserted into a cavity. A channel tube through which an accessory is to be inserted extends within the insertion portion. The distal end portion of the channel tube is arranged within a distal end rigid portion as a distal end forming portion on the distal end portion of the insertion portion. Moreover, an image pick-up unit configured to pick up an observation image is built in the distal end rigid portion. The channel tube and the image pick-up unit are arranged parallel with each other and extend in the axial direction in the distal end rigid portion.
In Jpn. Pat. Appln. KOHYO Publication No. 2003-511140, it is disclosed that the inner peripheral surface of a channel tube is formed into various shapes in the cross section orthogonal to the axial direction in order to improve an operability in moving forward and backward an accessory in the channel tube and secure a sufficient fluid flow.